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 * Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.net;

/**
 * Defines the <em>standard</em> socket options.
 *
 * <p> The {@link SocketOption#name name} of each socket option defined by this
 * class is its field name.
 *
 * <p> In this release, the socket options defined here are used by {@link
 * java.nio.channels.NetworkChannel network} channels in the {@link
 * java.nio.channels channels} package.
 *
 * @since 1.7
 */

public final class StandardSocketOptions {

  private StandardSocketOptions() {
  }

  // -- SOL_SOCKET --

  /**
   * Allow transmission of broadcast datagrams.
   *
   * <p> The value of this socket option is a {@code Boolean} that represents
   * whether the option is enabled or disabled. The option is specific to
   * datagram-oriented sockets sending to {@link java.net.Inet4Address IPv4}
   * broadcast addresses. When the socket option is enabled then the socket
   * can be used to send <em>broadcast datagrams</em>.
   *
   * <p> The initial value of this socket option is {@code FALSE}. The socket
   * option may be enabled or disabled at any time. Some operating systems may
   * require that the Java virtual machine be started with implementation
   * specific privileges to enable this option or send broadcast datagrams.
   *
   * @see <a href="http://www.ietf.org/rfc/rfc919.txt">RFC&nbsp;929: Broadcasting Internet
   * Datagrams</a>
   * @see DatagramSocket#setBroadcast
   */
  public static final SocketOption<Boolean> SO_BROADCAST =
      new StdSocketOption<Boolean>("SO_BROADCAST", Boolean.class);

  /**
   * Keep connection alive.
   *
   * <p> The value of this socket option is a {@code Boolean} that represents
   * whether the option is enabled or disabled. When the {@code SO_KEEPALIVE}
   * option is enabled the operating system may use a <em>keep-alive</em>
   * mechanism to periodically probe the other end of a connection when the
   * connection is otherwise idle. The exact semantics of the keep alive
   * mechanism is system dependent and therefore unspecified.
   *
   * <p> The initial value of this socket option is {@code FALSE}. The socket
   * option may be enabled or disabled at any time.
   *
   * @see <a href="http://www.ietf.org/rfc/rfc1122.txt">RFC&nbsp;1122 Requirements for Internet
   * Hosts -- Communication Layers</a>
   * @see Socket#setKeepAlive
   */
  public static final SocketOption<Boolean> SO_KEEPALIVE =
      new StdSocketOption<Boolean>("SO_KEEPALIVE", Boolean.class);

  /**
   * The size of the socket send buffer.
   *
   * <p> The value of this socket option is an {@code Integer} that is the
   * size of the socket send buffer in bytes. The socket send buffer is an
   * output buffer used by the networking implementation. It may need to be
   * increased for high-volume connections. The value of the socket option is
   * a <em>hint</em> to the implementation to size the buffer and the actual
   * size may differ. The socket option can be queried to retrieve the actual
   * size.
   *
   * <p> For datagram-oriented sockets, the size of the send buffer may limit
   * the size of the datagrams that may be sent by the socket. Whether
   * datagrams larger than the buffer size are sent or discarded is system
   * dependent.
   *
   * <p> The initial/default size of the socket send buffer and the range of
   * allowable values is system dependent although a negative size is not
   * allowed. An attempt to set the socket send buffer to larger than its
   * maximum size causes it to be set to its maximum size.
   *
   * <p> An implementation allows this socket option to be set before the
   * socket is bound or connected. Whether an implementation allows the
   * socket send buffer to be changed after the socket is bound is system
   * dependent.
   *
   * @see Socket#setSendBufferSize
   */
  public static final SocketOption<Integer> SO_SNDBUF =
      new StdSocketOption<Integer>("SO_SNDBUF", Integer.class);


  /**
   * The size of the socket receive buffer.
   *
   * <p> The value of this socket option is an {@code Integer} that is the
   * size of the socket receive buffer in bytes. The socket receive buffer is
   * an input buffer used by the networking implementation. It may need to be
   * increased for high-volume connections or decreased to limit the possible
   * backlog of incoming data. The value of the socket option is a
   * <em>hint</em> to the implementation to size the buffer and the actual
   * size may differ.
   *
   * <p> For datagram-oriented sockets, the size of the receive buffer may
   * limit the size of the datagrams that can be received. Whether datagrams
   * larger than the buffer size can be received is system dependent.
   * Increasing the socket receive buffer may be important for cases where
   * datagrams arrive in bursts faster than they can be processed.
   *
   * <p> In the case of stream-oriented sockets and the TCP/IP protocol, the
   * size of the socket receive buffer may be used when advertising the size
   * of the TCP receive window to the remote peer.
   *
   * <p> The initial/default size of the socket receive buffer and the range
   * of allowable values is system dependent although a negative size is not
   * allowed. An attempt to set the socket receive buffer to larger than its
   * maximum size causes it to be set to its maximum size.
   *
   * <p> An implementation allows this socket option to be set before the
   * socket is bound or connected. Whether an implementation allows the
   * socket receive buffer to be changed after the socket is bound is system
   * dependent.
   *
   * @see <a href="http://www.ietf.org/rfc/rfc1323.txt">RFC&nbsp;1323: TCP Extensions for High
   * Performance</a>
   * @see Socket#setReceiveBufferSize
   * @see ServerSocket#setReceiveBufferSize
   */
  public static final SocketOption<Integer> SO_RCVBUF =
      new StdSocketOption<Integer>("SO_RCVBUF", Integer.class);

  /**
   * Re-use address.
   *
   * <p> The value of this socket option is a {@code Boolean} that represents
   * whether the option is enabled or disabled. The exact semantics of this
   * socket option are socket type and system dependent.
   *
   * <p> In the case of stream-oriented sockets, this socket option will
   * usually determine whether the socket can be bound to a socket address
   * when a previous connection involving that socket address is in the
   * <em>TIME_WAIT</em> state. On implementations where the semantics differ,
   * and the socket option is not required to be enabled in order to bind the
   * socket when a previous connection is in this state, then the
   * implementation may choose to ignore this option.
   *
   * <p> For datagram-oriented sockets the socket option is used to allow
   * multiple programs bind to the same address. This option should be enabled
   * when the socket is to be used for Internet Protocol (IP) multicasting.
   *
   * <p> An implementation allows this socket option to be set before the
   * socket is bound or connected. Changing the value of this socket option
   * after the socket is bound has no effect. The default value of this
   * socket option is system dependent.
   *
   * @see <a href="http://www.ietf.org/rfc/rfc793.txt">RFC&nbsp;793: Transmission Control
   * Protocol</a>
   * @see ServerSocket#setReuseAddress
   */
  public static final SocketOption<Boolean> SO_REUSEADDR =
      new StdSocketOption<Boolean>("SO_REUSEADDR", Boolean.class);

  /**
   * Linger on close if data is present.
   *
   * <p> The value of this socket option is an {@code Integer} that controls
   * the action taken when unsent data is queued on the socket and a method
   * to close the socket is invoked. If the value of the socket option is zero
   * or greater, then it represents a timeout value, in seconds, known as the
   * <em>linger interval</em>. The linger interval is the timeout for the
   * {@code close} method to block while the operating system attempts to
   * transmit the unsent data or it decides that it is unable to transmit the
   * data. If the value of the socket option is less than zero then the option
   * is disabled. In that case the {@code close} method does not wait until
   * unsent data is transmitted; if possible the operating system will transmit
   * any unsent data before the connection is closed.
   *
   * <p> This socket option is intended for use with sockets that are configured
   * in {@link java.nio.channels.SelectableChannel#isBlocking() blocking} mode
   * only. The behavior of the {@code close} method when this option is
   * enabled on a non-blocking socket is not defined.
   *
   * <p> The initial value of this socket option is a negative value, meaning
   * that the option is disabled. The option may be enabled, or the linger
   * interval changed, at any time. The maximum value of the linger interval
   * is system dependent. Setting the linger interval to a value that is
   * greater than its maximum value causes the linger interval to be set to
   * its maximum value.
   *
   * @see Socket#setSoLinger
   */
  public static final SocketOption<Integer> SO_LINGER =
      new StdSocketOption<Integer>("SO_LINGER", Integer.class);

  // -- IPPROTO_IP --

  /**
   * The Type of Service (ToS) octet in the Internet Protocol (IP) header.
   *
   * <p> The value of this socket option is an {@code Integer} representing
   * the value of the ToS octet in IP packets sent by sockets to an {@link
   * StandardProtocolFamily#INET IPv4} socket. The interpretation of the ToS
   * octet is network specific and is not defined by this class. Further
   * information on the ToS octet can be found in <a
   * href="http://www.ietf.org/rfc/rfc1349.txt">RFC&nbsp;1349</a> and <a
   * href="http://www.ietf.org/rfc/rfc2474.txt">RFC&nbsp;2474</a>. The value
   * of the socket option is a <em>hint</em>. An implementation may ignore the
   * value, or ignore specific values.
   *
   * <p> The initial/default value of the TOS field in the ToS octet is
   * implementation specific but will typically be {@code 0}. For
   * datagram-oriented sockets the option may be configured at any time after
   * the socket has been bound. The new value of the octet is used when sending
   * subsequent datagrams. It is system dependent whether this option can be
   * queried or changed prior to binding the socket.
   *
   * <p> The behavior of this socket option on a stream-oriented socket, or an
   * {@link StandardProtocolFamily#INET6 IPv6} socket, is not defined in this
   * release.
   *
   * @see DatagramSocket#setTrafficClass
   */
  public static final SocketOption<Integer> IP_TOS =
      new StdSocketOption<Integer>("IP_TOS", Integer.class);

  /**
   * The network interface for Internet Protocol (IP) multicast datagrams.
   *
   * <p> The value of this socket option is a {@link NetworkInterface} that
   * represents the outgoing interface for multicast datagrams sent by the
   * datagram-oriented socket. For {@link StandardProtocolFamily#INET6 IPv6}
   * sockets then it is system dependent whether setting this option also
   * sets the outgoing interface for multicast datagrams sent to IPv4
   * addresses.
   *
   * <p> The initial/default value of this socket option may be {@code null}
   * to indicate that outgoing interface will be selected by the operating
   * system, typically based on the network routing tables. An implementation
   * allows this socket option to be set after the socket is bound. Whether
   * the socket option can be queried or changed prior to binding the socket
   * is system dependent.
   *
   * @see java.nio.channels.MulticastChannel
   * @see MulticastSocket#setInterface
   */
  public static final SocketOption<NetworkInterface> IP_MULTICAST_IF =
      new StdSocketOption<NetworkInterface>("IP_MULTICAST_IF", NetworkInterface.class);

  /**
   * The <em>time-to-live</em> for Internet Protocol (IP) multicast datagrams.
   *
   * <p> The value of this socket option is an {@code Integer} in the range
   * {@code 0 <= value <= 255}. It is used to control the scope of multicast
   * datagrams sent by the datagram-oriented socket.
   * In the case of an {@link StandardProtocolFamily#INET IPv4} socket
   * the option is the time-to-live (TTL) on multicast datagrams sent by the
   * socket. Datagrams with a TTL of zero are not transmitted on the network
   * but may be delivered locally. In the case of an {@link
   * StandardProtocolFamily#INET6 IPv6} socket the option is the
   * <em>hop limit</em> which is number of <em>hops</em> that the datagram can
   * pass through before expiring on the network. For IPv6 sockets it is
   * system dependent whether the option also sets the <em>time-to-live</em>
   * on multicast datagrams sent to IPv4 addresses.
   *
   * <p> The initial/default value of the time-to-live setting is typically
   * {@code 1}. An implementation allows this socket option to be set after
   * the socket is bound. Whether the socket option can be queried or changed
   * prior to binding the socket is system dependent.
   *
   * @see java.nio.channels.MulticastChannel
   * @see MulticastSocket#setTimeToLive
   */
  public static final SocketOption<Integer> IP_MULTICAST_TTL =
      new StdSocketOption<Integer>("IP_MULTICAST_TTL", Integer.class);

  /**
   * Loopback for Internet Protocol (IP) multicast datagrams.
   *
   * <p> The value of this socket option is a {@code Boolean} that controls
   * the <em>loopback</em> of multicast datagrams. The value of the socket
   * option represents if the option is enabled or disabled.
   *
   * <p> The exact semantics of this socket options are system dependent.
   * In particular, it is system dependent whether the loopback applies to
   * multicast datagrams sent from the socket or received by the socket.
   * For {@link StandardProtocolFamily#INET6 IPv6} sockets then it is
   * system dependent whether the option also applies to multicast datagrams
   * sent to IPv4 addresses.
   *
   * <p> The initial/default value of this socket option is {@code TRUE}. An
   * implementation allows this socket option to be set after the socket is
   * bound. Whether the socket option can be queried or changed prior to
   * binding the socket is system dependent.
   *
   * @see java.nio.channels.MulticastChannel
   * @see MulticastSocket#setLoopbackMode
   */
  public static final SocketOption<Boolean> IP_MULTICAST_LOOP =
      new StdSocketOption<Boolean>("IP_MULTICAST_LOOP", Boolean.class);

  // -- IPPROTO_TCP --

  /**
   * Disable the Nagle algorithm.
   *
   * <p> The value of this socket option is a {@code Boolean} that represents
   * whether the option is enabled or disabled. The socket option is specific to
   * stream-oriented sockets using the TCP/IP protocol. TCP/IP uses an algorithm
   * known as <em>The Nagle Algorithm</em> to coalesce short segments and
   * improve network efficiency.
   *
   * <p> The default value of this socket option is {@code FALSE}. The
   * socket option should only be enabled in cases where it is known that the
   * coalescing impacts performance. The socket option may be enabled at any
   * time. In other words, the Nagle Algorithm can be disabled. Once the option
   * is enabled, it is system dependent whether it can be subsequently
   * disabled. If it cannot, then invoking the {@code setOption} method to
   * disable the option has no effect.
   *
   * @see <a href="http://www.ietf.org/rfc/rfc1122.txt">RFC&nbsp;1122: Requirements for Internet
   * Hosts -- Communication Layers</a>
   * @see Socket#setTcpNoDelay
   */
  public static final SocketOption<Boolean> TCP_NODELAY =
      new StdSocketOption<Boolean>("TCP_NODELAY", Boolean.class);


  private static class StdSocketOption<T> implements SocketOption<T> {

    private final String name;
    private final Class<T> type;

    StdSocketOption(String name, Class<T> type) {
      this.name = name;
      this.type = type;
    }

    @Override
    public String name() {
      return name;
    }

    @Override
    public Class<T> type() {
      return type;
    }

    @Override
    public String toString() {
      return name;
    }
  }
}
